Visual signal for photographic cameras



May 28, 1963 c. B. ESTES 3,091,167

VISUAL SIGNAL FOR PHOTOGRAPHIC CAMERAS Original Filed Sept. 10, 1959 2Sheets-Sheet 1 CameronB. Estes May 28, 1963 c. B. ESTES VISUAL SIGNALFOR PHOTOGRAPHIC CAMERAS 2 Sheets-Sheet 2 Original Filed Sept. 10, 1959Cameron B. Estes INVENTOR- ATTORNEYS United States Patent 3 Claims. (Cl.95--64) The present application is a divisional application of mycopending parent application Serial No. 839,104, filed September 10,1959.

The present invention relates to photographic cameras having automaticexposure control systems, and more particularly relates to means forindicating low scene brightness in such cameras.

It is convenient for the operator of a motion picture camera, which hasan automatic exposure control system, to be warned when scene brightnessdrops below the range for which the camera is designed. Numerous deviceshave been proposed for presenting a low-light signal to the cameraoperator in such cases. However, signals of this type generally havebeen illuminated by scene light, the intensity of which has diminishedwhen the signal must be effective.

It is therefore a primary object of the present invention to warn theoperator of a camera, which has an automatic exposure control system,when the scene brightness is less than a predetermined value, by meansof a visual signal that does not depend on scene light for illumination.

A further object of the invention is to display any of the foregoingsignals in the viewfinder of a camera.

Another object of the invention is to present an artificiallyilluminated image of an aperture scale in the viewfinder of a camerahaving an automatic exposure control system and having means controlledby such system for moving the imaged scale or its pointer to correspondto scene brightness.

Other objects of the invention will appear from the followingdescription, reference being made to the accompanying drawings, wherein:

FIG. 1 is a schematic right side view of the basic elements of a motionpicture camera embodying one form of the present invention;

FIG. 2 is a front view of the diaphragm vane illustrated in FIG. 1;

FIG. 3 is the apparent view seen by the camera operator looking throughthe viewfinder of a camera provided with the invention in the form shownin FIGS. 1 and 2;

FIG. 4 is a further embodiment of structure for presenting an image ofan aperture scale in the viewfinder;

FIG. 5 is a front view of the diaphragm vane illustrated in FIG. 4;

FIG. 6 is the apparent view seen by the operator of a camera providedwith the indicating structure shown in FIGS. 4 and 5; and

FIG. 7 is a front view of a further form of diaphragmvane indicatingmechanism which may be employed as a part of the invention.

Referring to FIG. 1, a typical camera embodying the invention has ataking-lens axis 10 on which are arranged a taking-lens system indicatedgenerally at 14, a diaphragm vane 12, a shutter 20 and a photosensitivesurface such as 'a filmstrip 22. Referring also to FIG. 2. the diaphragmvane may be formed as a disk pivoted centrally on a shaft 16 and havinga tapered, curved aperture 18, which moves in a path crossing the lensaxis 10 for establishing an exposure aperture whose area 3,091,167Patented May 28, 1963 is a function of the angular position of thediaphragm vane. The diaphragm vane may be positioned automatically, in amanner well known in the art, by means of a galvanometer coil 24, whichis connected to and rotates the diaphragm shaft 16. Coil 24 cooperateswith a permanent magnet core 26 and is connected by leads 28 and 30 to aphotocell 32, which is exposed to scene light. Variations in scenebrightness cause the coil 24 to be variably energized by photocell 32and thereby cause the coil to move angularly about shaft 16 forestablishing an angular position of the diaphragm vane 12. correspondingto scene brightness. The structure and operation of the galvanometer andphotocell are well known in the art and may be of the type disclosed inUS. Patent 2,509,893, granted May 30, 1950, to C. F. Taylor et al.

Although the drawings illustrate a motion picture camera wherein theexposure is automatically controlled by positioning a diaphragm vane, itwill be understood that the invention has equal utility in conjunctionwith other forms of automatic exposure control, e.g., in still or motionpicture cameras wherein shutter speed is automatic-ally controlledinstead of or in addition to diaphragm opening.

Referring to FIG. 2, a transparent segment 34 set into the periphery ofthe vane 12 has signal control means in the form of an aperture scale36, an image of which is transmitted into the viewfinder 38 (FIG. 1) ofthe camera in accordance with one form of the invention. The image ofthe aperture scale is artificially illuminated by an electric lamp 40which is connected in circuit with a camera operating switch 42, asource of electrical potential, which is illustrated as a battery 44,and an electrically operated motor 46. This motor may be used fordriving the film advance mechanism and the shutter mechanism in a mannerwell known in the art. When the camera operating switch 42 is closed,the drive motor 46 and lamp 40 are energized.

Light from lamp 40 passes through a diffuser 48, the aperture scale 36and a relay lens 50. This light is reflected by a pair of mirrors 52 and54 to a viewing locus, which is illustrated as a telescopic viewfinder38 having an objective 55, a centrally disposed pair of erector lenses56 separated by a diaphragm 57 having an aperture 58, a field stop 59having a framing aperture 60 and a scale aperture 62, and an eyepiece64. The scale image reflected from mirror 54 is transmitted through theerector lenses 56 and the aperture 58 of diaphragm S7 and rearwardlythrough the scale aperture 62 of the field stop 59 into the eyepiece 64.The scale image and field frame appear through the viewfinder asillustrated in FIG. 3.

FIG. 4 illustrates an alternate embodiment of the structure shown inFIG. 1. In this embodiment, light from lamp 40 passes through a pinholeaperture 78 in a baffle plate 80, and passes through an aperture scale136 (FIG. 5) in a transparent arcuate segment 134 on the periphery ofthe diaphragm vane 212. The image of scale 136 is inverted because ofthe pinhole aperture and is reflected into the viewfinder by mirrors 52and 54 in the same manner as described in relation to FIG. 1. -In FIG.4, the field stop 159 forward of the eyepiece 64 is provided with arectangular field aperture 160 (see also FIG. 6) and with a smallcircular scale aperture 162, which displays only a single aperture valuefrom the image of scale 136.

A further form of signal control means is shown in FIG. 7, wherein thediaphragm vane 212 is provided with a peripheral notch 82, which may beused to cooperate With the lamp such as 40 in FIGS. 1 and 4. In thisembodiment, there is no aperture scale on the diaphragm vane; instead,notch 82 merely permits light from the lamp to be transmitted into theviewfinder when a low-light condition exists and blocks such light atall other times. Obviously, provided With an ear rather than a notch, sothat light will be excluded from the view finder only when the lowlightcondition exists.

This invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected Within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

I claim:

1. In a camera having an automatic exposure control system including aphotocell and a member moved automatically under control of saidphotocell as a function of scene brightness to regulate the exposure offilm in said camera, the combination comprising: means including anelectric lamp and a source of electrical potential for said lamp fortransmitting light to a viewing locus visible from outside of thecamera; signal control means comprising a scale device disposed incooperative relation with said transmitting means and moved by saidmember for modifying the light transmitted to said locus in accordancewith the position of said member, said scale device having areas ofcontrasting light transmission defining scale indicia and having a pathof movement intersecting the light transmitted to said locus; and abafile having a pinhole aperture interposed between said lamp and thepath of said scale device.

2. In a camera having an automatic exposurecontrol system including aphotocell and a member moved autothe diaphragm vane may be.

matically under control of said photocell as a function of scenebrightness to regulate the exposure of film in said camera, thecombination comprising: means including an electric lamp and a source ofelectrical potential for said lamp for transmitting light to a viewinglocus visible from the outside of the camera; and signal control meansdisposed in cooperative relation with said transmitting means and movedby said member for modifying the light transmitted to said locus inaccordance with the position of said member, and said signal controlmeans comprising a discontinuity in the periphery of said moving member,said discontinuity having a path intersecting the light transmitted tosaid locus.

3. In a camera having an automatic exposure control system including aphotocell and a diaphragm vane moved automatically under control of saidphotocell as a function of scene brightness to regulate the exposure offilm in said camera, the combination comprising: means including anelectric lamp and a source of electrical potential for said lamp fortransmitting light to a viewing locus visible from the outside of thecamera; and signal control means comprising a notch in the periphery ofsaid vane disposed in cooperative relation with said transmitting meansand moved by said member in timed relation therewith through a path ofmovement intersecting the light transmitted to said locus for modifyingthe light transmitted to said locus in accordance with the position ofsaid member.

2,297,262 Tonnies Sept. 29, 1942

1. IN A CAMERA HAVING AN AUTOMATIC EXPOSURE CONTROL SYSTEM INCLUDING APHOTOCELL AND A MEMBER MOVED AUTOMATICALLY UNDER CONTROL OF SAIDPHOTOCELL AS A FUNCTION OF SCENE BRIGHTNESS TO REGULATE THE EXPOSURE OFFILM IN SAID CAMERA, THE COMBINATION COMPRISING: MEANS INCLUDING ANELECTRIC LAMP AND A SOURCE OF ELECTRICAL POTENTIAL FOR SAID LAMP FORTRANSMITTING LIGHT TO A VIEWING LOCUS VISIBLE FROM OUTSIDE OF THECAMERA; SIGNAL CONTROL MEANS COMPRISING A SCALE DEVICE DISPOSED INCOOPERATIVE RELATION WITH SAID TRANSMITTING MEANS AND MOVED BY SAIDMEMBER FOR MODIFYING THE LIGHT TRANSMITTED TO SAID LOCUS IN ACCORDANCEWITH THE POSITION OF SAID MEMBER, SAID SCALE DEVICE HAVING AREAS OFCONTRASTING LIGHT TRANSMISSION DEFINING SCALE INDICIA AND HAVING A PATHOF MOVEMENT INTERSECTING THE LIGHT TRANSMITTED TO SAID LOCUS; AND ABAFFLE HAVING A PINHOLE APERTURE INTERPOSED BETWEEN SAID LAMP AND THEPATH OF SAID SCALE DEVICE.